Surgical stapler

ABSTRACT

A surgical stapler comprises a hollow shaft  10  and a tube  92  slidable axially within the shaft between a forward position wherein one end  96  of the tube projects beyond a free end of the shaft to enter a puncture site in a blood vessel and a rearward position wherein the end of the locator tube is retracted within the shaft. A surgical staple  40  straddles the tube  92  and is slidable thereon forwardly towards an anvil  24  against which the staple may be deformed to staple together the opposite edges of the puncture site. A cam mechanism drives the staple forwardly along the tube  92  into deforming engagement with the anvil and at the same time retracts the tube into the shaft in time to allow the legs of the staple to close onto the puncture site.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 10/455,768filed Jun. 4, 2003, which is a continuation of application Ser. No.09/948,813, filed Sept. 7, 2001, entitled “Surgical Stapler,” whichclaims priority to Ireland Application No. S2000/0722, filed Sept. 8,2000 and Ireland Application No. S2000/0724, filed Sept. 8, 2000, eachof which are hereby incorporated by reference in their entirety.

FIELD OF THE INVENTION

The present invention relates to an instrument, herein called a surgicalstapler, for closing a puncture in a liquid-carrying vessel by applyinga staple across the puncture so as to effect a closure. The inventionrelates particularly to surgical staplers for closing punctures in bloodvessels.

BACKGROUND TO THE INVENTION

When performing catheterisation procedures, such as angiography orangioplasty, a catheter is generally introduced into the vascular systemby first penetrating the skin, underlying tissues and blood vessel witha sharpened hollow needle. Next, a guidewire is commonly insertedthrough the lumen of the hollow needle and is caused to enter theselected blood vessel. Subsequently the needle is typically stripped offthe guidewire and a combination of a dilator and/or introducer (or anintroducer alone) are fed over the guidewire and pushed through the skinto enter the blood vessel. The guidewire can then be removed and adesired catheter to carry out the procedure is fed through the lumen ofthe introducer and advanced through the vascular system until theworking end of the catheter is appropriately positioned. Following theconclusion of the catheterisation procedure the working catheter will bewithdrawn and subsequently the dilator and/or introducer will also beremoved from the wound. Following this procedure the vessel puncturemust be closed in order to prevent loss of blood through the puncturehole.

Typically the wound is closed by maintaining external pressure over thevessel until the puncture naturally seals. This procedure can takeapproximately 30 minutes with the length of time usually being greaterif the patient is hypertensive or anticoagulated. The procedure can alsobe uncomfortable for the patient and involves costly professional timeon the part of the hospital staff. Other pressure techniques such aspressure bandages, sandbags or clamps have been employed but these alsoinvolve ensuring the patient remains motionless for an extended periodof time and is monitored to ensure the effectiveness of the procedure.

A number of devices have been developed in recent times which provide anobstruction in the area of the puncture in order to prevent bleeding.For example, U.S. Pat. Nos. 4,852,568 and 4,890,612 disclose a devicewhich utilises a collagen plug which when placed at the blood vesselopening absorbs body fluids, swells and affects a seal. Other plug likedevices, for example U.S. Pat. Nos. 5,222,974 and 5,282,827, describe aplug and anchor device, the anchor being positioned inside the vesseland the collagen plug outside the vessel thereby sandwiching thepuncture between both and effecting a closure.

WO 98/17179 discloses a surgical stapler having a blood locator tubeadjacent the stapling head. A guidewire passes through an opening at theend of the tube and up through a hollow bore in the tube, so that thestapler can be fed onto the guidewire and down onto the puncture site.When the device reaches the puncture site, the tip of the tube entersthe blood flow within the artery and blood passes through the tube andout of the distal end at a point visible to the clinician. The cliniciancan then actuate the stapling mechanism in the knowledge that thestapling head is at the puncture site in the arterial wall.

It is an object of the present invention to provide an instrument forclosing a puncture in a liquid-carrying vessel by stapling.

SUMMARY OF THE INVENTION

According to one exemplary embodiment of the present invention, asurgical stapler is provided having a shaft, a locator slidable axiallyof the shaft between a forward position wherein the locator projectsbeyond a free end of the shaft to enter a puncture site in aliquid-carrying vessel in a human or animal, thereby to locate the freeend of the shaft at the puncture site, and a rearward position whereinthe locator is retracted relative to the shaft, a surgical staplestraddling the locator and slidable forwardly thereon, said staplehaving forwardly pointing legs disposed respectively on opposite sidesof the locator, an anvil against which the staple may be deformed tostaple together opposite edges of the puncture site, and an actuator fordriving the staple forwardly along the locator into deforming engagementwith the anvil and for retracting the locator in co-ordination with themovement of the staple such that the locator is withdrawn from betweenthe legs of the staple in time to allow the legs of the staple to stapletogether opposite edges of the puncture site.

In another aspect the invention provides a method of stapling closed apuncture site in a liquid-carrying vessel in a human or animal body,comprising the steps of: introducing a stapling mechanism to thelocation of the vessel; positioning the stapling mechanism at thepuncture site by means of a locator associated with the staplingmechanism and projecting forwardly thereof, the locator sensing theposition of the puncture site by entering the vessel at the site;delivering a staple to, and deforming the staple to close, the puncturesite; and in co-ordination with the delivery and deformation of thestaple, withdrawing the locator from the puncture site such that thelocator is fully withdrawn from the vessel by the time the staple isfully deformed to close the puncture site. Preferably, the steps ofdelivering and deforming the staple and in co-ordination therewithwithdrawing the locator are effected by operating a single control on astapler actuating mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention will now be described, by way ofexample, with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of an embodiment of a surgical stapleraccording to the invention;

FIG. 1(A) is an enlarged perspective view of the free end of the shaftof the stapler of FIG. 1;

FIG. 2 is a perspective view of the stapler of FIG. 1 with the left-handside handle removed;

FIG. 3 is a perspective view of the stapler of FIG. 1 with theright-hand side handle and shaft removed;

FIG. 4 is an exploded perspective view of the components seen in FIG. 3further omitting the left-hand side handle;

FIG. 5 is an exploded perspective view of the internal components at thefree end of the shaft;

FIG. 6 is a perspective view of the internal components at the free endof the shaft in the pre-fire position and omitting the left-hand side ofthe shaft;

FIG. 7 is a side elevation of the components of FIG. 6 in the pre-fireposition;

FIG. 8 is a front elevation of the components of FIG. 6 in the pre-fireposition;

FIG. 9 is a perspective view of the internal components of the free end,showing the position of the components in mid-cycle with fully formedstaple;

FIG. 10 is a side elevation of the components of FIG. 9 in the post-fireposition;

FIG. 11 is a perspective view of the blood locator tube with enlargedviews of the front and rear portions, FIG. 11A and FIG. 11Brespectively;

FIG. 12 is a side sectional elevation of the front portion of analternative embodiment of the blood locator tube of the stapler;

FIG. 13 is a perspective view of the front portion of the blood locatortube shown in FIG. 12;

FIG. 13(A) is a perspective view of the front portion of an alternativeembodiment of the blood locator tube shown in FIG. 12;

FIG. 14(A) is a perspective view of the surgical staple in the pre-fire(pre-deformed) state;

FIG. 14(B) is a perspective view of the surgical staple in the post-fire(deformed) state;

FIG. 15 is an enlarged perspective view of the cam mechanism;

FIG. 16 is a side elevation of the cam mechanism;

FIG. 17 is a side elevation of the shaft section of the device andsuction port; and

FIG. 18 is an end view of the surgical staple, locator tube and insert.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, an exemplary stapler can include a rigidshaft 10 extending from a moulded plastic housing 12 shaped in the formof a pistol-like handle. The shaft 10, which is hollow to accommodatevarious moving components to be described, comprises right and left-handsides 10A, 10B respectively which are secured together at the distalfree end by a section of heat shrinkable tubing 91 in combination withinterference pins and mating cavities 15A and 15B (FIGS. 4 and 5) alongthe edges of the distal tip, and at the proximal end by pins 17A matingin an interference fit with corresponding cavities 17B (FIG. 2 and 3)captured within the housing 12. Likewise, the housing 12 comprises leftand right-hand sides 12A, 12B respectively.

The major part of the exposed length of the shaft 10 has a constantcircular cross-section, but at its free end the shaft 10 has a portion14 of increased diameter having a “bullet” profile. One end of thisbullet portion 14 is tapered down toward a staple exit slot 16 while theother end is tapered down to the remaining section of the shaft, whichextends back into the housing 12. The ratio of the maximum diameter ofthe bullet portion 14 to the diameter of the remaining section ofexposed shaft is approximately 5:4. Heat shrink sleeve 91 sits flushwith the surface of the bullet portion 14, to ensure a traumatic entry,percutaneously, into the tissue.

The reason for the bullet profile is so that the shaft 10 is asatraumatic as possible during introduction to the body to minimise theamount of force and tissue dilation required when tracking the devicepercutaneously over a guidewire 18 and onto the surface of a bloodvessel adjacent a puncture hole, as will be described. In an alternativeembodiment, not shown, the bullet portion 14 is oval in cross-sectionwith the major axis of the oval being coincident with the staple exitslot 16, so as to minimise the circumferential length for a given staplewidth.

The bullet portion 14 of the shaft 10 houses a staple 40 and a stapledelivery mechanism (FIGS. 4 to 7). The staple delivery mechanismcomprises a tiltable anvil 24 and a pair of rod-like actuating members,namely an elongated anvil support 30 and an elongated staple former 52,the latter being slidable in the shaft 10 and operated by atrigger-operated cam mechanism 62 in the handle housing 12.

The anvil 24 has a pair of upstanding fingers 24A at the front and apair of downwardly inclined tilt arms 24B at the rear. The anvil 24 istiltably mounted in the bullet portion 14 by a pair of wings 26 whichare pivotable in recesses 28 in the right-hand side 10A of the shaft 10(the wings 26 are retained in the recesses by the underside ofprojections 54 on the former 52).

Tilting of the anvil 24 is effected by the cam mechanism 62 via theanvil support 30, which is slidable axially within the right-hand shaftside 10A in channel 32. The front end of the anvil support 30 isbifurcated to form two arms 34 having lateral projections 36 (FIGS. 6and 7). The arms slide in rebates 38 in the right-hand shaft side 10A.The anvil support 30 is movable, by the cam mechanism 62, from a forwardposition, FIGS. 6 and 7, wherein the arms 34 extend under the anvil'ssupport wings 25 to support the anvil forming fingers 24A directly infront of a surgical staple 40 to be delivered, to a rearward position,FIG. 10, wherein the arms 34 are withdrawn under the downwardly inclinedtilt arms 24B at the rear of the anvil 24 so as to tilt the anvilanti-clockwise (as seen in FIG. 10) and displace the fingers 24A out ofthe path of the staple 40. The angle of incline of tilt arms 24B may beincreased to cause separation of the two shaft halves, in addition todisplacing the fingers 24A out of the path of the formed staple, to aidin staple release. This is achieved by the anvil (in its fully tiltedposition) applying pressure to the underside of former 52 and the uppersurface of the right shaft 10A.

Referring additionally to FIGS. 11, 11A and 11B, a hollow blood locatortube 92 is slidable axially within the shaft 10 in a channel 44 in theanvil support 30 and in an opposing U-shaped channel 53 in the stapleformer 52. The tube 92 extends the full length of the shaft 10 and has aconstant, generally oval or elongated cross-section, except at itsdistal tip 14 where the locator tube 92 is formed into a narrow opening96 and at a crimped region 94 towards the rear of the tube 92 which isformed to allow only the guidewire 18 and not blood to exit the rear ofthe locator tube.

Under the action of the cam mechanism 62 the tube 92 is slidable axiallyin the shaft 10 between a forward position, FIGS. 6 and 7, wherein itsfront end projects beyond the bullet portion 14 of the shaft 10 underthe influence of a leaf spring 88 to be described, and a rearwardposition, FIGS. 9 and 10, wherein the front end of the tube 92 isretracted within the bullet portion 14 behind the fingers 24A of theanvil 24 during the rotation of cam 62.

The purpose of the blood locator tube 92 is to follow a previouslyplaced guidewire 18 to a puncture site in a blood vessel, thereby tolocate the free end of bullet portion 14 of the shaft 10 against theexterior wall of the blood vessel at the puncture site. To properlylocate the bullet portion 14 the front end of the tube 92 must actuallypenetrate the blood vessel wall at the puncture site and this isindicated by blood flowing back through the tube 92 and out through ablood outlet port 93 (FIG. 11) in the tube. A channel (not shown) in thepart of the left-hand side 10B of the shaft 10 within the housing 12provides communication between the port 93 and a blood exit port 50(FIG. 1) on the side of the housing 12B, so that the blood flowing backthrough the tube 92 is visible at the exterior of the housing.

A blood exit port adapter 51 (FIG. 1) may be secured into the opening ofthe blood exit port 50 via a matching male luer taper 51A to enhance thevisibility of the exiting blood. The blood exit port adapter has areduced internal diameter, relative to the opening of the blood exitport 50, which for a constant blood flow increases the pressure ofexiting blood causing a jet effect of exiting blood.

In the absence of the blood exit port adapter, the blood exit port'sfemale luer taper opening matches that of the standard medical syringe'smale luer taper making it possible at any time during the device's useto inject fluid via the blood exit port into the lumen of the locatortube to exit at its distal tip. This may be necessary from time to timeto clear the locator tube's lumen of congealed blood and of trapped softtissue. Alternatively, radiopaque contrast medium may be injected viathe locator tube to confirm the relative location of the locator tube'sdistal tip to that of the blood vessel wall by fluoroscopy, or anyinjectable fluids may be injected for diagnostic or therapeutic reasons.

The blood outlet port 93 is sized to have a minimum area correspondingto the available blood entry area at the distal tip; however, isnarrower (in a transverse aspect) than the diameter of the guidewire 18to prevent the guidewire inadvertently exiting the blood outlet portduring insertion, instead of exiting from the intended proximal end ofthe locator tube.

It has been found that the naturally formed shape of puncture wounds inarterial walls is elongated rather than round. Whereas the hole isformed by introducing instruments generally of round cross section, thewall tends to open generally along a transverse line which lies in thedirection of the circumference of the artery (rather than along the axisof the artery). By having a generally oval blood locator tube, thelocator tube (when introduced by the clinician with the major axis ofthe oval perpendicular to the axis of the artery), will fit morenaturally within the arterial opening. The consequence of this is thatthe wound edges which are to be stapled together, lie closer togetherthan if a tube of circular cross section were to be used.

This in turn has the consequence that the staple used need not be solarge, and in turn, the dimensions of the shaft, which must accommodatethe staple when in its unformed state, can be reduced, leading to lesstrauma for the tissue into and from which the shaft is introduced.

A further consequence of having a generally oval or elongated crosssection for the locator tube is that the tube will be more disposed tothe centre of the puncture than with a rounded tube. The presentembodiment has a staple which straddles the locator tube, therebyincreasing the likelihood of the staple closing the elongated wound atits centre rather than towards one or other of the extremities of thewound.

The opening 96 at the front of the tube 92 has an approximately circularportion 96A at the extreme forward tip of the tube which is of greaterdiameter than the width of the remaining portion 96B of the opening 96.The portion 96B is in the form of a slot which is aligned with the majoraxis of the elongated cross-section of the tube 92 and slopes rearwardlyfrom the circular portion 96A. The guidewire 18, which passes throughthe tube 92, FIG. 11, is chosen to be of sufficiently smaller diameterthan the diameter of the opening 96A at the front end of the tube 92 forthe guidewire 18 to be easily inserted into the tube 92 and pass throughthe opening 96A. However, the guidewire is also chosen to be too largeto fit within the remainder 96B of the opening 96. In this way guidewire18 is constrained to remain in opening 96A, and the size of opening 96Asets an upper limit on the diameter of guidewire which can be used withthe device. One could introduce a narrow neck or constriction into theopening 96 just above opening 96A (at the points indicated by 96C) toensure that very small guidewires were constrained within the enlargedopening 96A, but in general this is unnecessary as the guidewire willnormally be supplied with the device, or the device will only besupplied for use with a particular gauge of guidewire.

The rear crimp 94 and tip opening 96A are positioned to encourage theguidewire to lie along the bottom curved surface of the tube, i.e. thatportion of the tube lying in a direct line between the opening in thecrimped end and the opening 96A. This helps prevent guidewire 18 fromlaying up against the inside of blood exit port 93 and preventing egressof blood, FIG. 11A and 11B.

The curvilinear nature of opening 96 increases the available inlet areato match that of the available area within the body of the locator tubewith the guidewire 18 in situ.

The slot-like opening 96B slopes away from the circular opening 96A forease of insertion into the vessel opening and to reduce the potential oftrauma to the inner wall of the vessel opposite the opening beingstapled. This is achieved because the guidewire 18 protruding fromopening 96A will tend to push the opposite wall of the vessel away fromthe locator tube tip, and the point at which the guidewire protrudes(due to it being constrained in the opening 96A) is the farthest partforward of the tip. Thus, the shape of the tip is streamlined away fromopening 96A to prevent any part of the tip gouging into or otherwisedamaging the inner vessel walls. Also, the peripheral edges 95 of theopening 96 are bent inwardly to as to avoid sharp edges which mightdamage soft tissue and the vessel wall.

The distal end of an alternative embodiment of a locator tube 42 isshown in FIGS. 12 and 13. This embodiment also has a substantiallyconstant elongated cross-section, which in this case converges to anapproximately circular guidewire opening 46 at the extreme forward tipof the tube. The guidewire 18, which passes through the tube 42, isusually chosen to be of sufficiently smaller diameter than the diameterof the opening 46 for there to be an adequate gap for the blood to passback through the tube 42 even in the presence of the guidewire. However,further openings 46A are provided in opposite sides of the tube 42 justbehind the front opening 46 to allow more ready access of the blood tothe interior of the tube in cases where the guidewire 18 may not leave alarge enough gap for passage of blood solely through the opening 46. Thethree openings 46, 46A, 46A in fact form respective portions of a singlefront opening, being in reality three connected lobes, all connected byconstricted channels 47, and all in communication with the interior ofthe tube.

An alternative embodiment is shown in FIG. 13(A) where the threeopenings 46, 46A and 46A, while collectively constituting the frontopening of the tube 42, are independent of each other. Again, opening 46at the front of the tube is sized to receive a maximum size of guidewireand openings 46A are sized to allow a sufficient flow of blood to enterthe locator tube.

A problem can arise in devices of this type where an oversized guidewireis used which occludes the hollow interior of the blood locator tube andthereby prevents blood flow back through the tube. To prevent thissituation the lobe 46 through which the guidewire emerges in the tip ofthe tube of FIGS. 12, 13 and 13A is of a lesser diameter than theinternal bore of the tube. The dimensions of this lobe 46 set a maximumfor the guidewire diameter for use with the device, and ensure that evenwhen this maximum diameter guidewire is used, there is still sufficientinternal clearance within the tube bore to allow a strong blood flowthrough the tube from the other lobes 46A.

The staple 40 straddles the blood locator tube 92 within the bulletportion 14 of the shaft 10, see FIGS. 6 and 8, and is slidable thereonforwardly towards the free end of the bullet portion 14. In particular(see also the enlarged view of FIG. 14), the staple 40 comprises a backor base portion 40A from which extend perpendicularly at each endrespective legs 40B which terminate in sharpened points. The baseportion 40A and legs 40B lie in substantially a common plane except fora centre portion 40C of the base portion 40A which is deformed in adirection perpendicular to the legs 40B so as to have an Ω (omega) shapegenerally complementary to the external cross-sectional profile of theblood locator tube 92 and internal cross-section of an insert 160, to bedescribed. The base section 40A is pre-bent to between 150° and 170° atpoints A and B equidistant from the centre of the base, positioned tomaximise the closure of the closed staple (and is relevant to the depthof forming wings 54 on the former 52). The base section is also deformedat points C & D so as to narrow the cross sectional width of the wire atboth points thereby directing the staple to bend at these points. Thestaple 40 is mounted on the blood locator tube 92 such that the centreportion 40C of the staple sits on the upper half of the tube 92, as seenin FIG. 6 and 8, where the narrow open section of the omega shape isapproximately equal to the width of the tube and with the legs 40Bpointing forwardly on opposite sides of the tube 92. The depth of thecentre portion 40C of the staple 40 is such that the legs 40B of thestaple lie substantially directly on opposite sides of the central axisof the tube 92. This will ensure that the staple 40 is positionedcentrally across the puncture hole in the blood vessel. In order toavoid the guidewire 18 fouling the staple 40 when the latter is closedon the puncture site, the hole 96A is offset below the plane containingthe legs 40B of the staple, FIG. 8.

The metal insert 160 is received in a recess in the left-hand shaft side10B within the bullet section 14. The insert 160 provides mechanicalsupport for the omega section 40C of the staple 40 during the stapleforming process and is engaged by the former 52 during the stapleejection phase of the process so as to separate both halves of thebullet section for easy staple release. The insert is profiled togenerally correspond with the external profile of the omega shapedportion 40C of the staple. At the distal end the insert profile tapersdown to closely approximate the omega-shaped portion of the staple 40C(FIG. 18). This has the effect of offering mechanical support to theomega-shaped portion of the staple during the staple forming process,during which the base section is bent about the anvil fingers. Thisbending motion in turn causes the omega to open up or flatten out. Themetal insert prevents this from happening only allowing the staple baseto deform around the anvil. The omega interlock system between thestaple 40 and insert 160 (FIG. 18) also stabilises the staple,vertically, within the staple exit plain during the forming process,whilst allowing easy staple release once formed, due to the relativelysmall contact area between staple and insert.

The staple former 52 has a cross-section conforming to that of the bloodlocator tube 92 and is slidable on the blood locator tube 92 axiallywithin the shaft 10. The former 52 is located behind the staple 40 onthe tube 92 and is operated by the cam mechanism 62. At its front endthe former 52 has a pair of forming arms 54 which are so shaped that,when the former 52 is driven forward by the cam mechanism 62, the staple40 is driven against and deformed around the anvil fingers 24A so thatthe legs 40B of the staple close together (FIG. 9) onto the puncturesite. The surface of the forming arms which contact the staple 55 may beso profiled to match the cross-sectional geometry of the staple. Thismatching profile stabilises the staple on the forming surfaces of theforming arms 54 during the high pressure contact with the staple duringstaple forming and closure. During the forward movement of the staple,the staple legs slide toward the anvil 24 along a track defined by thestaple exit slot 16 between the opposite halves the bullet portion 14.The slot 16 provides a slight interference fit on the staple legs 40B toprevent the staple 40 moving forward during storage of the device orprior to firing. The slot 16 further prevents the staple rotating in thehorizontal plane (FIG. 7 and 10) during its forward travel. Once formingof the staple around the anvil is completed the forming force is removedfrom the former 52 by a drop-off in the cam, the anvil is lowered andthe former advanced again to eject the staple from the device. Duringthis forward movement (ejection phase), the sloped edges 52A and 52B ofthe former engage with the metal insert 160 to prise open the bulletsection of the shaft assembly thus facilitating staple release.

The cam mechanism 62 can be seen in FIG. 3 and in enlarged views ofFIGS. 15 and 16. The mechanism 62 consists of a first cam 58 and asecond cam 60 mounted on a common axis 62 which sits in a recess 64 inthe left-hand side 10A of the shaft (FIG. 4) and a corresponding recess(not shown) in the right-hand side 10B. Trigger 56 is similarly mountedin the shaft by a pair of stub axles 66 which are received in a triggerseating recess 68 in each half of the shaft 10, FIG. 4.

An actuating pin 70 extends through the first and second cams 58, 60.This actuating pin is acted on by a cam actuating surface 72 (FIG. 3)provided on the trigger 56, so that when the trigger is squeezed theactuating surface moves the actuating pin in an anticlockwise directionaround the axis 62. Because the actuating pin extends through both cams58, 60 of the mechanism 62, the cams are both rotated simultaneouslythrough the same angle as determined by the trigger squeeze. The use ofthis cam mechanism ensures accurate timing and positive mechanicaldisplacements of all the moving components and accurate movement of thecomponents relative to each other. The geometry of the trigger pivotpins 66 and actuating surface 72 relative to the cam pivot 62 and camactuating pin 70 is configured to minimise the trigger rotation to only23 degrees whilst the cam rotates a total of 90 degrees. Thisconfiguration also provides a mechanical advantage that the triggerdelivers to the cam-actuating pin 70 of approximately 1:4. This geometryis further configured to deliver the best mechanical advantage at thephase during the staple forming cycle, which requires the highestforming forces, having the advantage of minimising the trigger effortand ensuring a constant trigger effort over the full cycle. Trigger 56further comprises a ratchet lever 73B, shown in FIG. 3, which engageswith ratchet strip 73A, which is mounted in the right handle 12A, FIG.3. This non-return ratchet system ensures the firing cycle of the stapleis uninterrupted, non-repeatable and provides a positive indication thatthe device has been used.

Referring back to FIG. 3, a leaf spring 88 positioned in a recess in theleft-hand side 10A of the shaft and a corresponding recess (not shown)in the right-hand side 10B. The free ends of the spring are formed intoa loop so as to pivot freely in the curved corner recesses in which itsits and to aid assembly. The apex of this spring is positioned in aslot 74 in the crimped portion 94 of the blood locator tube 92 thusassuming the role of cam follower for the blood locator tube. This bloodlocator tube cam follower 74 is acted on by the first cam 58. Similarly,the first cam 58 acts on a former cam follower 76, whereas the secondcam 60 acts on anvil-support cam followers 78A and 78B. The shape of thefirst and second cams 58, 60 are shown in elevation in FIG. 16 (thesecond cam 60 is shown in dotted outline as it is concealed by the firstcam). FIG. 16 also shows actuating pin 70, and a reinforcing strut 80mounted between the first and second cams diametrically opposite theactuating pin 70.

The cams are shown in the starting positions in FIG. 15 and 16.Squeezing the trigger fully (through an angle of 23 degrees) causes thecams to rotate anticlockwise through 90 degrees.

The apex of the leaf spring 88 which engages with and operates as a camfollower for the blood locator tube (leaf spring apex) acts against therear surface 82 of the first cam 58. As the first cam rotatesanticlockwise from the position shown in FIG. 15, the distance betweenthe blood locator tube cam follower 74 and the axis 62 is increased.This causes the blood locator tube to be drawn backwards as the triggeris squeezed.

The former cam follower 76 acts against the front surface 84 of thefirst cam 58. Again the distance between former cam follower 76 and axis62 increases through the initial stages of the trigger being squeezed.The profile of surface 84 is designed with two distinct non-linearefficiencies, transitioned from low mechanical efficiency/highdisplacement to high mechanical efficiency/low displacement. The firstrise rate being for displacement of the staple from its startingposition to initial forming against the anvil, which requires thelargest displacement of the staple with minimal load. The secondnon-linear rise rate is designed to correlate the cams mechanicalefficiency with the load profile required to form the closed staple,minimising the trigger effort required and ensuring a constant triggereffort over the full cycle. A V-shaped section 84A of front section 84causes the former 52 to momentarily suspend its forward motion when thestaple has been fully formed. The effect of this is to momentarilyrelease the pressure off the formed staple against the anvil, allowingthe anvil to be dropped. The geometry of the distal tip of the former isdesigned to provide sufficient intrinsic spring tension to allow theforming arms 54 to further squeeze the formed staple, once the anvil hasdropped, to further closed the formed staple. As the cam continues torotate the raised profile 84B on the cam causes the former to advanceforward again, ejecting the staple clear of the device.

It can be seen that a raised hump 82A on the profile of the rear surface82 of the first cam is located almost diametrically opposite theV-shaped section 84A. The reason for this is to increase the rate atwhich the blood locator tube is drawn out of the puncture site justbefore the staple is fully formed and released. The intention is toleave the tube in the puncture as late as possible to provide supportfor the walls of the blood vessel for as long as possible And also toensure that the head of the device remains centred over the puncturehole. The blood locator tube 92 is biased forward by the blood locatortube leaf spring 88 which also maintains pressure between the apex ofthe spring and the rear surface 82 of the first cam 58.

The blood locator tube leaf spring 88 allows the locator tube to bedisplaced in a proximal direction (back into the shaft of the device)against the spring tension in the event that the locator tube meets anysignificant resistance during insertion of the device, to preventunnecessary trauma to soft tissues, the vessel or its rear wall.

An example of where this is particularly useful is if the stapler isadvanced too far into the vessel, so that the tip of the tube 92 meetsthe inner wall. The blood locator tube will then be displaced back intothe shaft, and may be designed to protrude through the end of the handlehousing to give a visual indication that the device has been insertedagainst the wall. Furthermore, the device may be designed so that theblood outlet port 93 on the tube 92 is brought out of registry with theblood exit port 50 in the handle housing when the tube is displacedbackwards, so that the clinician will note the flow of blood ceasingwhen the tube meets the inner vessel wall in this way.

The cam mechanism 62, however, provides positive mechanicaldisplacements for withdrawing the locator tube at the appropriatetiming, to ensure there is no chance of the staple being formed whilstthe locator tube is in a forward position and potentially interferingwith the staple formation.

A further reason to leave the blood locator tube in the puncture hole aslate as possible is that the continued retraction of the tube everts orturns outwards the opposed edges of the puncture wound and aidspenetration of the staple legs into the arterial wall. Eversion of theedges of the puncture helps prevent thrombus formation within thevessel. Yet another reason to leave the blood locator tube in thepuncture hole as late as possible is to ensure that the stapler headremains centred over the hole during the staple delivery process. Whenthe locator tube is fully retracted, only the guidewire is left withinthe wound, and this will be easily retracted from the closed wound afterthe stapler has been removed from the puncture site.

The anvil-support cam follower 78B acts against the rear surface 90 ofthe second cam 60. It can be seen that this rear surface 90 provides thegreatest increase in distance relative to the axis to the section 90Afrom about 60 to 90 degrees below the horizontal. The reason for this isthat the anvil is maintained in place until the staple has been formedand the pressure on the former has been relaxed slightly to allow theanvil to drop. The anvil is maintained in place for the initial 60degrees of rotation by the anvil-support cam follower 78A being incontact with cam surface 98 of cam 60, preventing the anvil-support 30from moving from its starting position. The cam surface 98 for the first60 degrees of cam rotation is at a constant distance from the cam axle62 (in dwell).

In use, the stapler is initially in the “pre-fire” configuration shownin FIGS. 6 to 8. The front end of the blood locator tube 92 is in afully forward position projecting beyond the free end of the bulletportion 14 of the shaft 10, the anvil-support 30 is in a fully forwardposition with its arms 36 extending under the anvil's support wings 25ensuring the anvil fingers 24A are directly in front of the staple 40,the former 52 is in a fully retracted position away from the anvilfingers 24A, and the staple 40 is in its fully back position up againstthe forming arms 54.

In this configuration the external end of a previously positionedguidewire 18 is inserted into the hole 96A in the front end of the bloodlocator tube 92 and fed through the tube 92 until it exits a guidewireexit port at the rear of the housing 12. The stapler is now fed alongthe guidewire 18 until the tip 95 of the tube 92 enters the blood vessellumen through the vessel's puncture hole. This is indicated by bloodflowing out of the blood exit port 50 or, if present, the adapter 51. Atthis point the front end of the bullet portion 14 of the shaft 10 willbe resting against the exterior wall of the blood vessel.

Now the trigger 56 is squeezed, causing the cams of the cam mechanism 62to rotate through 90 degrees. As mentioned, the rear end of each of theblood locator tube 92, anvil-support 30 and former 52 are coupled to thecam mechanism via cam followers and the following co-ordinated movementof these components takes place as the cams rotate through 90 degrees.

(A).

0 degrees: Stapler in pre-fire configuration.

32 degrees: Former 52 forward sufficiently to clamp staple against anvilfingers 24A, blood locator tube begins to retract. At this point thestaple legs will have punctured the wall of blood vessel, but the stapleis not yet fully deformed.

50 degrees: Former 52 forward sufficiently to deform the staple legsaround the anvil fingers 24A and close the staple on the puncture site:blood locator tube 42 fully retracted. At some point between 32 and 50degrees, the blood locator tube will have withdrawn from between thestaple legs in time to allow them to close. This should be left as lateas possible to provide support for the walls of the blood vessel for aslong as possible.

65 degrees: Clamp force released from staple (due to drop off in camprofile). Anvil support 30 starting to retract.

75 degrees: Anvil support 30 retracted sufficiently to act against anvilsloped tilt arms 24B. Anvil fingers 24A begin to drop.

83 degrees: Anvil support 30 fully retracted. Anvil fingers 24A droppeddown to allow release of staple. Intrinsic tension in former arms 54further closes the staple. Former 52 begins to move forward again toeject staple. Former 52 begins to interfere with the insert 160 tospread bullet portion 14 of the shaft to allow for clear staple release.

90 degrees: Former 52 fully forward; staple ejected from the device.

The use of cams in cam mechanism 62 ensures the accuracy of sequence andrelative timing between events as well as ensuring positive mechanicaldisplacements of all components.

In a further embodiment to the above described device, on the completionof the cycle described above, further rotation of the cam causes theanvil support 30 to return to its fully forward position, lifting theanvil fingers 24A to their raised position behind the formed staplebeing held in forming arms 54. The former is then retracted in aproximal direction (back into the shaft) causing the rear of the closedstaple to crash into the raised anvil fingers 24A, to be positivelyejected from within the forming arms 54 and the device. The additionalmovements of the anvil support and former may be facilitated byadditional cam lobes on cam 58; or alternatively spring driven, assistedand timed by appropriately positioned radial slots in cam 58 to allowingthe cam follower of the anvil support to move forward and the camfollower of the former to move rearwards.

In a further embodiment the trigger activates an automatic firing cycle,not shown. A tension spring attached to the cams is released from itsextended state so as to rotate the actuation cam through a 90 degree arccausing the same component movements as described above.

In an alternative embodiment, not shown, once the staple has been formedthe forward end of the former 52 retracts and engages pull arms on theanvil-support 30 causing it to move in a rearward direction. As it doesso, it engages with the rear end of the anvil 24, which is angleddownward into the path of the moving slide. Centrally opposed wingsextend from the anvil and are located so as to pivot in opposed wingslots formed in the right-hand side 10A of the shaft. Once engaged withthe slide the rear end of the anvil is pushed upward causing it to pivotabout the wings and arc the forward end of the anvil downward. As itdoes so, it disengages from the staple so that the device can be removedfrom the puncture tract along the guidewire.

In a further embodiment the reverse profile 82 on the first cam 58 whichengages with the cam follower 74 on the blood locator tube 92 isextended so that when the staple forming cycle is completed the firstcam continues to rotate causing the blood locator tube to move furtherin a proximal direction. At its distal end the blood locator tube haswings which as it moves in a proximal direction engages with the pullarms of the anvil-support 30 causing it to move in a proximal directionand engage the anvil tilt arms thereby disengaging the distal end of theanvil from the formed staple. In this embodiment the second cam isredundant and can be omitted.

In a further embodiment, FIG. 17, the bullet head 14 of the shaft 10,which approximates the blood vessel wall 208, includes a number ofsuction ports 200. These ports are in communication with a suctionadapter 202 via capillaries 204 within the shaft section. Suction, froma standard wall suction outlet or independent suction pump, is suppliedto the suction adapter 202 via an on/off tap 206. Once the device is inposition on the arterial wall, as indicated by blood flowing from theblood exit port, the tap 206 is turned to the “on” position therebydelivering suction to the ports 200 on the bullet head 14. This in turnsuctions the blood vessel wall 208 against the face of the head 14 so asto stabilise it during delivery of the staple. Once delivered thesuction is deactivated so as to remove the device from the blood vesselwall and tissue tract.

The invention is not limited to the embodiments described herein and maybe modified or varied without departing from the scope of the invention.

1. A surgical stapler comprising a shaft, a locator slidable axially ofthe shaft between a forward position wherein the locator projects beyonda free end of the shaft to enter a puncture site in a liquid-carryingvessel in a human or animal, thereby to locate the free end of the shaftat the puncture site, and a rearward position wherein the locator isretracted relative to the shaft, a surgical staple straddling thelocator and slidable forwardly thereon, said staple having forwardlypointing legs disposed respectively on opposite sides of the locator, ananvil against which the staple may be deformed to staple togetheropposite edges of the puncture site, and an actuator for driving thestaple forwardly along the locator into deforming engagement with theanvil and for retracting the locator in co-ordination with the movementof the staple such that the locator is withdrawn from between the legsof the staple in time to allow the legs of the staple to staple togetheropposite edges of the puncture site.